The present invention relates generally to the construction of interfaces between computers and data transmission media and, more particularly, to a construction for an interface interconnecting a Personal Computer Modem Card ("PCMC") with a telephone line or other transmission medium.
A presently available interface between a "personal" computer and a telephone line may include a (1) Personal Computer Modem Card, (2) length of cable, and (3) Data Access Arrangement. The Personal Computer Modem Card may also be referred to as a "PCMC," "Personal Computer Modern Card International Association card," "PCMCIA card," "PCM card," or, simply, "modem card." The Data Access Arrangement may also be referred to as a "Direct Access Arrangement," "DAA," PSTN INTERFACE," or, simply, "access arrangement."
The PCMC includes a computer socket and cable connector and may slide into an access opening of the computer. The computer socket of the PCMC matingly engages a corresponding socket in the computer. The cable connector on the PCMC is attached to one end of the length of cable. Data from the computer is received by the PCMC through the socket, modulated, and then transmitted through the length of cable.
The DAA is interconnected to the cable and includes an RJ style jack (such as an RJ11 jack) interconnected to the telephone line. The DAA receives signals via the cable and responsively transmits a data signal, through the jack, onto the telephone line. Signals from the telephone line to the computer flow, of course, in the opposite direction.
The DAA also provides a degree of electrical isolation for the PCMC and computer. If the voltage along the telephone line should spike to a high level (as might happen if lightening should strike the telephone network), the voltage at the DAA's cable connector would still be relatively low. As a result, the PCMC and computer would be protected from damage by the voltage surge.
The length of cable between the PCMC and DAA may extend for a foot or more. Such an arrangement (sometimes colloquially described in the United States as a "soap on a rope" interface) is found by many manufacturers to be relatively difficult and expensive to mass produce. Further, such an arrangement may be unreliable in providing a continuous physical interconnection between a computer and a telephone line. For example, the weight of the DAA and cable may exert pressure on the PCMC, physically pulling the cable away from the PCMC cable connector.
Further, such an arrangement is bulky. Many users choose to work with portable computers because of their low weight, small size, and easy portability. A large cable and DAA assembly makes a computer and its related equipment less portable and, thus, less useful to the person employing the computer.
Furthermore, many prior art mechanisms may be connected improperly to the computer. For example, the cable may be improperly attached to the fragile PCMC, or the DAA may be improperly connected to the cable. Such incorrect connections obviously prevent the computer from communicating with the telephone network until the missconnection is noted and changed. In an extreme case, an improper connection may damage the computer. Many presently available mechanisms also lack a reliable system for guiding the cable, DAA, and PCMC into a correct alignment for firmly, but releasably, ensuring that the PCMC and DAA are kept in communication with each other.